The exoskeleton of crustaceans consists of chitin biopolymers where the embedded inorganic biominerals, mainly CaCO₃, affect strongly its mechanical properties. Raman and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopies and Transmission Electron Microscopy (TEM) are applied to investigate the CaCO₃ structure in various parts of the Calappa granulata crab exoskeleton. The shape of the main Raman peak of CaCO₃ reveals the presence of two phases which are identified as calcite and amorphous calcium carbonate (ACC). The relative concentration of the two phases in various parts of the exoskeleton is determined from the area ratio under the corresponding peaks. The results of the Ca L_3,2-edge NEXAFS analysis are in line with the Raman findings, since the energy separation of peaks that appear in the lower frequency region of the main L₂ and L₃ peaks due to crystal field splitting, is directly related to the percentage of the ACC phase in the total CaCO₃ mineral content. The C K-edge spectra are used for the determination of the extent of calcification of the exoskeleton. Furthermore, dark and bright field TEM images reveal the presence of nanocrystallites with an average size of 20 nm. The structure of the nanocrystallites, as derived from the Selected Area Electron Diffraction patterns, is calcite. The results suggest that ACC plays a structural role in the exoskeleton of Calappa granulata.

甲壳类动物的外骨骼由几丁质生物聚合物组成，其中嵌入的无机生物矿物，主要是 CaCO ₃，强烈影响其机械性能。拉曼和近边缘 X 射线吸收精细结构 (NEXAFS) 光谱和透射电子显微镜 (TEM) 被应用于研究Calappa granulata蟹外骨骼各个部分的 CaCO ₃结构。CaCO ₃的主拉曼峰的形状揭示了两相的存在，它们被确定为方解石和无定形碳酸钙（ACC）。两相在外骨骼各部位的相对浓度由相应峰下的面积比确定。Ca L _3,2的结果-edge NEXAFS 分析与拉曼结果一致，因为由于晶体场分裂而出现在主L ₂和L ₃峰的低频区域的峰的能量分离与 ACC 相的百分比直接相关在总 CaCO ₃矿物质含量中。C K边缘光谱用于确定外骨骼的钙化程度。此外，明场和暗场 TEM 图像显示存在平均尺寸为 20 nm 的纳米微晶。源自选定区域电子衍射图案的纳米微晶的结构是方解石。结果表明 ACC 在外骨骼中起结构作用卡拉帕颗粒。